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Airlines that fly the Boeing 737 Max have continued to move the aircraft during its grounding, frequently flying empty planes between bases around the world.
The flights come as airlines seek to rationalize their fleets in preparation for its return to service after more than five months of grounding following two deadly crashes.
However, airlines' Boeing 737 Max planes remain scattered across different airports and countries, with some unable to bring their entire fleets back together, and many aircraft remaining far from home.
The planes are still being maintained and moved regularly, airlines told Business Insider, with carriers avoiding putting them into long-term storage and keen to use them as soon as possible as costs pile up.
The Max was grounded around the world in March after two crashes killed a total of 346 people.
Airlines which fly the Boeing 737 Max have continued to move the aircraft during its grounding, frequently flying empty planes between locations around the world, seeking to rationalize their fleets in preparation for its return to service after more than five months out of action following two deadly crashes.
The Max was grounded around the world in March after a second crash involving an Ethiopian Airlines 737 Max killed 157 people. It followed a crash involving Lion Air flight in Indonesia which left 189 dead. In total, 346 people were killed across the two crashes, leading to global outrage, and the eventual grounding.
Since the grounding, airlines have spent much time attempting to get the planes back to their home bases.
Many have secured permission from national transport bodies to "ferry" the planes — flying them with airline crew but with no passengers on board — back to where they could be kept together and maintained as airlines wait for the 737 Max to return to service.
Some planes have run into trouble during this process. In June, a Norwegian Boeing 737 Max plane was forced to land in France after Germany denied it entry to its airspace.
The plane was trying to move from Spain back to the airline's base in Sweden, in what a spokesman for Norwegian told Business Insider was an effort to keep all of its planes closer together for easy maintenance and an easier upgrade to the planes when Boeing's fix is approved.
The plane was in France for 11 days before it was then allowed to fly on, a Norwegian spokesman told Business Insider.
This ferrying process has left planes spread around the world, with the majority of airlines unable to keep their entire fleet of 737 Max planes together.
While some Max planes are gathered together in airlines' main base airports, other airlines have left their planes across multiple countries where they will be available to fly again when the grounding is finally lifted.
In some cases, airlines are keeping their Max planes in multiple airports across their home country, some in airports and others in sites the airlines use for storage and maintenance.
Business Insider contacted more than a dozen airlines with 737 Max planes in their fleets to find out about their whereabouts and movements since the grounding. Here is what the eight airlines that provided responses said:
Trans-European airline TUI said that one of its Max planes is in the Canary Islands, which are off the coast of north-west Africa. It will remain there until the "grounding is lifted," the spokesman added. 14 of its 15 Max planes are at their "home bases in their respective countries."
FlyDubai, a budget airline based in the UAE, said one of its in-service planes is being stored at a maintenance facility in the US, where it was when the grounding came into effect. The rest of its 737 Max planes are spread between two airports in Dubai, Dubai International Airport and Al Maktoum International Airport.
Norwegian, which has one of Europe's largest fleets of 737 Max, said that its aircraft are being stored across three capital cities in Scandinavia: Oslo in Norway, Stockholm in Sweden, and Helsinki in Finland. The three hubs are "where they [the 737 Max planes] primarily operated before the grounding of the aircraft."
American Airlines said the airline's 24 Max planes are being stored across the US. 14 are at its maintenance base in Tulsa, Oklahoma, and 10 are in the airline's storage facility in Roswell, New Mexico. It said the airline "ferried aircraft to these locations after the aircraft was grounded."
Canadian airline WestJet said that its 13 Max planes are being kept in airports in Calgary, Toronto and Vancouver, which are three of the airline's hubs. The airline said that under Canadian law, it was able to move the planes with no one on board.
It brought three Max planes from Florida to Canada after the planes were grounded, a spokeswoman said, and has since ferried the planes across Canada for maintenance.
Aerolíneas Argentinas said that its five max planes are being kept in Argentina, with two in Ezeiza International Airport in Buenos Aires, and the other three in Aeroparque Jorge Newbery, a domestic airport. They were already in Argentina when the planes were grounded, a spokesperson said.
Southwest, meanwhile, has all of its 34 Max planes in one location, Southern California Logistics Airport in Victorville, California, having ferried the planes there from across the US when the grounding was ordered.
One of Southwest's planes made an emergency landing in Florida when it was being moved in March, but the FAA said that the plane did not experience the same software malfunction that took place in both fatal crashes, The Associated Press reported.
United Airlines said this week that it was in the process of ferrying its 737 Max fleet to a single location, an airport in Phoenix, Arizona. It has 14 737 Max planes, which are being moved from their current locations in Los Angeles and Houston. United said it has been granted permission for the flights by the FAA.
United put the moves down to "several reasons — notably Arizona having more favorable weather conditions to store aircraft and to prevent a potential hurricane threat to those aircraft currently located in Houston."
Airlines are keeping their planes ready to fly again with little notice
Airlines are largely reluctant to move their planes into long-term storage, which can mean draining vital fluids or partial disassembly of the aircraft for preservation purposes. Such storage could slow up the process of returning the planes to service after the 737 Max is un-grounded.
Instead of placing the aircraft into long-term storage, airlines are regularly moving and maintaining the planes, getting them ready to be used as soon as the grounding is lifted — even as the timeline for its return is continually pushed back.
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How airlines are storing their 737 Max fleet varies substantial from company to company. WestJet said its Max planes "continue to receive regularly scheduled maintenance checks, the engines on each aircraft are being run every seven days and we have been taxiing them on aprons around our hangars to keep them moving."
"We have no plans to store them," its spokeswoman said.
FlyDubai said it is following a care and maintenance plan on its grounded planes "in line with the documented standards and procedures set by Boeing" as they wait in the airports.
Southwest said its planes are in "active storage" as they sit outside in the airport in Victorville, California.
TUI said that its planes are "typically" kept parked outside in the airport but added that their storage is "at the airport's discretion."
Norwegian did not reveal its storage plans, but said that its 737 Maxs have been "positioned so that they can easily be reintroduced to the operation once the grounding has been lifted."
Most airlines have avoided placing their 737 Max fleets into hangars, which would provide more protection from the elements but come at a bigger cost, and could represent a longer-term storage plan.
Airlines are keen for the plane to return to the air as soon as possible, as storing and maintaining the planes is a costly task.
The financial hit has been compounded for many airlines as they have been forced to reduce routes and cancel flights while the plane remains on the ground, as well as deal with the delayed deliveries of their new Boeing planes.
Many airlines, including Ryanair, Korean Air, and Air Europa, are yet to receive the Boeing 737 Max planes that they ordered.
The undelivered planes, meanwhile, have been piling up at Boeing Seattle facility, even as Boeing slowed production after the fatal crashes. Boeing has even started storing the planes in its employee parking lot as the crisis persists.
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